U.S. patent application number 12/246015 was filed with the patent office on 2009-04-23 for roller transport conveyor and method.
This patent application is currently assigned to DEMATIC CORP.. Invention is credited to Mark S. Harkema, Wayne A. Moshauer, Thanh V. Nguyen, Dennis J. Schuitema.
Application Number | 20090101475 12/246015 |
Document ID | / |
Family ID | 40562349 |
Filed Date | 2009-04-23 |
United States Patent
Application |
20090101475 |
Kind Code |
A1 |
Nguyen; Thanh V. ; et
al. |
April 23, 2009 |
ROLLER TRANSPORT CONVEYOR AND METHOD
Abstract
A roller transport conveyor and method provides a device for
conveying items along a plurality of rollers, in which the device
may be set up and operated and serviced by manually raising and
lowering one or more contact members that transmit force from a
spring to urge a drive belt into contact with an underside of the
rollers. The contact member is adjustable by raising and lowering
the contact member to expand and contract the spring, or by raising
and lowering a base on which the spring is supported, so that the
drive belt may be engaged with and disengaged from the rollers. A
gravity take-up includes a mass suspended from a cable that is
routed to a pulley having the drive belt reeved thereon. The cable
is wound upon a winch that compensates for belt stretch, or for
belts of various lengths.
Inventors: |
Nguyen; Thanh V.; (Wyoming,
MI) ; Schuitema; Dennis J.; (Ada, MI) ;
Harkema; Mark S.; (Grand Rapids, MI) ; Moshauer;
Wayne A.; (Rockford, MI) |
Correspondence
Address: |
VAN DYKE, GARDNER, LINN & BURKHART, LLP
SUITE 207, 2851 CHARLEVOIX DRIVE, S.E.
GRAND RAPIDS
MI
49546
US
|
Assignee: |
DEMATIC CORP.
Grand Rapids
MI
|
Family ID: |
40562349 |
Appl. No.: |
12/246015 |
Filed: |
October 6, 2008 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
60981965 |
Oct 23, 2007 |
|
|
|
Current U.S.
Class: |
198/617 ;
198/814; 198/815 |
Current CPC
Class: |
B65G 23/44 20130101;
B65G 21/14 20130101 |
Class at
Publication: |
198/617 ;
198/814; 198/815 |
International
Class: |
B65G 23/44 20060101
B65G023/44; B65G 47/00 20060101 B65G047/00 |
Claims
1. A transport conveyor comprising: a frame; a motor, said motor
supported at said frame; a plurality of rollers, said rollers
rotatably supported at said frame; an endless drive belt, said
drive belt adapted to drive said rollers; and a carriage assembly
supported at said frame, said carriage assembly comprising a
support member, a contact member, a spring, and a retraction
device; wherein said contact member is supported at said support
member and adapted to engage said drive belt, wherein said spring
is disposed between said support member and said contact member and
is adapted to bias said drive belt upwardly into contact with said
rollers, and wherein said retraction device is supported at said
support member and adapted to selectively retract said contact
member to lower said drive belt out of contact with said
rollers.
2. The transport conveyor of claim 1, wherein said retraction
device comprises a movable clasp for engaging said contact member
and retaining said contact member in a retracted position.
3. The transport conveyor of claim 2, further comprising a lever
operatively connected at said clasp for moving said clasp to permit
said retraction device to move to the extended position.
4. The transport conveyor of claim 1, wherein said retraction
device comprises an adjustable base at a bottom portion of said
spring, said adjustable base being biased between a retracted
position and an extended position relative to said support
member.
5. The transport conveyor of claim 4, wherein said retraction
device further comprises: an outer element having a passageway
through which said adjustable base is received, said adjustable
base being rotatable relative to said outer element; a spiral
channel at an inner surface of said outer element; and an axial
protrusion at an outer surface of said adjustable base; wherein
said axial protrusion is operatively received in said spiral
channel so that rotation of said adjustable base relative to said
outer element causes said adjustable base to telescopically extend
from said outer element.
6. The transport conveyor of claim 4, wherein said retraction
device further comprises a locking member at said adjustable base,
wherein said locking member engages said support member when said
retraction device is in the extended position to prevent said
support member from moving to the retracted position.
7. The transport conveyor of claim 6, wherein said locking member
prevents rotation of said retraction device relative to said
support member when said locking member is in said elevated
position.
8. The transport conveyor of claim 6, wherein said locking member
is disengageable from said support member to permit said retraction
device to move to the retracted-position.
9. The transport conveyor of claim 1, further comprising a gravity
take-up, said transport conveyor comprising: a mass supported at
said frame; a cable having a first end portion and a second end
portion, said cable adapted to support said mass in suspension,
wherein said first end portion is connected at said mass and said
second end portion is connected at said frame; a bracket assembly
at said frame, said bracket assembly adapted to engage said cable
between said first end portion and said second end portion; and a
pulley, said pulley being rotatably coupled to said bracket
assembly and engaging said endless drive belt; wherein said mass
imparts tension to said cable and said cable transmits the tension
to said belt via said bracket assembly.
10. The transport conveyor of claim 9, further comprising a winch
at said frame for windably receiving said cable at said second end
portion, wherein said winch is operable to shorten said cable to
thereby raise said mass.
11. The transport conveyor of claim 10, wherein said winch
comprises a ratcheting device to selectively prevent said cable
from unwinding from said winch.
12. The transport conveyor of claim 9, further comprising a first
sheave above said mass, a second sheave spaced horizontally from
said first sheave, a third sheave spaced horizontally and
vertically from said second sheave, and a fourth sheave spaced
horizontally from said third sheave at said bracket assembly,
wherein said cable is reeved around said sheaves.
13. The transport conveyor of claim 9, further comprising at least
one guide member, wherein said bracket assembly is adjustably
mounted at said at least one guide member.
14. A method of adjusting a gravity take-up for a transport
conveyor, said method comprising: providing a mass, a cable having
a first end portion and a second end portion, a bracket assembly, a
pulley, a sheave, and an endless belt; connecting the first end
portion of the cable at the mass; connecting the second end portion
of the cable at the conveyor; coupling the sheave to the bracket
assembly; coupling the pulley to the bracket assembly; reeving the
cable around the sheave between the first end portion and the
second end portion of the cable; reeving the belt around the
pulley; and suspending the mass above a surface to impart tension
to the belt via the cable, the sheave, the bracket assembly, and
the pulley.
15. The method of claim 14, wherein said connecting the second end
portion of the cable at the conveyor further comprises: providing a
winch at the conveyor; and winding the second end portion of the
cable at the winch.
16. A method of adjusting a transport conveyor, said method
comprising: providing a transport conveyor having a plurality of
rollers, a drive belt for driving said rollers, a support member, a
contact member, a spring, and a retraction device; positioning the
support member at the conveyor for supporting the contact member;
positioning the contact member at the support member for supporting
the drive belt; positioning the retraction device at the support
member and below the contact member; positioning the spring at the
retraction device; and raising at least a portion of the spring to
raise the contact member and engage the drive belt with the
rollers.
17. The method of claim 16, wherein said raising further comprises:
positioning the retraction device under the spring; and raising the
retraction device with respect to the support member.
18. The method of claim 17, wherein said raising further comprises:
providing a locking member that engages the support member when the
retraction device is in a raised position; and engaging the locking
member with the support member after raising the retraction device
with respect to the support member.
19. The method of claim 17, wherein said raising further comprises:
providing an outer element of the retraction device; providing an
inner adjustable base of the retraction device; providing a
passageway through the outer element; positioning the inner
adjustable base in the passageway of the outer element, the outer
element being rotatable relative to the adjustable base; providing
a spiral channel at an inner surface of the outer element;
providing an axial protrusion at an outer surface of the adjustable
base; positioning the axial protrusion in the spiral channel; and
rotating the outer element relative to the adjustable base to raise
the adjustable base relative to the outer element.
Description
CROSS-REFERENCE TO RELATED APPLICATION
[0001] The present application claims the benefit of U.S.
Provisional Application, Ser. No. 60/981,965, filed Oct. 23, 2007,
which is hereby incorporated herein by reference in its
entirety.
FIELD OF THE INVENTION
[0002] The present invention relates generally to powered conveyors
and, more particularly, to powered roller conveyors.
BACKGROUND OF THE INVENTION
[0003] Roller transport conveyors are known to include a plurality
of rollers for conveying objects such as packages thereon. The
rollers may be powered by a drive device such as an endless drive
belt that is driven by an electric motor or the like. A take-up
device may be used to apply tension to the endless drive belt.
SUMMARY OF THE INVENTION
[0004] The present invention provides a roller transport conveyor
that is suitable for continuously conveying articles along the
conveyor. The present invention provides a roller transport
conveyor that is relatively simple to assemble or set up,
disassemble, and maintain because it does not require pneumatic,
hydraulic, or other fluid power sources. The present invention
further provides a take-up that maintains constant tension on a
drive belt while facilitating adjustment of the take-up to account
for belt stretch and/or for belts of different lengths.
[0005] According to one aspect of the invention, a transport
conveyor conveys items in a direction of conveyance. A drive belt
is biased into frictional engagement with the rollers for driving
the rollers. A carriage assembly, including a support member, a
contact member, a spring, and a retraction device, is operable to
bias the drive belt upwardly to engage the rollers, and also to
disengage the drive belt from the rollers. The support member is
supported at the conveyor and the retraction device is movably
mounted thereto. The spring is supported at the retraction device
and the contact member is supported above the support member by the
spring. The retraction device is operable to raise and lower at
least a portion of the spring, which raises and lowers the contact
member. Lowering the contact member biases the drive belt out of
contact with the rollers.
[0006] The retraction device may be an adjustable base at a bottom
portion of the spring. The adjustable base is movable between a
lowered or retracted position and a raised or extended position
relative to the support member. In the retracted position the
spring is lowered so that the drive belt is no longer in frictional
contact with the rollers. For example, the adjustable base may be
rotatable relative to an outer element. The outer element has a
passageway through which the adjustable base is received. A spiral
channel at an inner surface of the outer element receives an axial
protrusion at an outer surface of the adjustable base. The axial
protrusion is operatively received in the spiral channel so that
rotation of the adjustable base relative to the outer element
causes the adjustable base to telescopically extend from the outer
element. Alternatively, an axial protrusion may be located at the
inner surface of the outer element and a spiral channel located at
the outer surface of the adjustable base.
[0007] The retraction device may include a locking member at the
adjustable base. The locking member engages the support member when
the retraction device is in the extended position, which prevents
the support member from inadvertently moving to the retracted
position. The locking member is disengageable from the support
member to permit the retraction device to move to the retracted
position, thereby lowering the spring and the contact member.
[0008] The retraction device may include a movable clasp located
adjacent the spring for retaining the contact member in the
retracted position. A lever is connected at the clasp for biasing
the clasp away from a catch at the contact member to permit the
contact member to move to the extended position.
[0009] According to another aspect, a gravity take-up is provided
for a transport conveyor. The gravity take-up includes a mass, a
cable, a bracket assembly, at least one sheave, and a pulley. A
first end portion of the cable is connected at the mass for
suspending the mass above a surface, and the second end portion is
connected at the conveyor. A drive belt is reeved upon the pulley,
which is rotatably mounted at the bracket assembly. The sheave is
rotatably mounted at the bracket assembly for engaging the cable.
The mass imparts tension to the cable, which transmits tension to
the belt via the sheave, the bracket assembly, and the pulley.
[0010] A plurality of sheaves may be incorporated for routing the
cable along a desired path or route. A winch may be provided at the
conveyor for windably receiving the cable at the cable's second end
so that the winch is operable to raise and lower the mass. The
winch may include a ratcheting device to prevent the cable from
unwinding. The gravity take-up and the drive belt may be serviced
by unwinding the cable from the winch until the mass is supported
on the surface, after which further unwinding imparts slack to the
cable and the drive belt.
[0011] These and other objects, advantages, purposes, and features
of the present invention will become apparent upon review of the
following specification in conjunction with the drawings.
BRIEF DESCRIPTION OF THE DRAWINGS
[0012] FIG. 1 is a perspective view of a portion of a conveyor bed
in accordance with the present invention;
[0013] FIG. 2A is a partially-exploded perspective view of a first
carriage assembly in accordance with the present invention and
having a support member and a contact member;
[0014] FIG. 2B is a top plan view of the carriage assembly of FIG.
2A;
[0015] FIG. 3 is a perspective view of the support member of FIG.
2;
[0016] FIG. 4 is a perspective view of a retraction device useful
with the support member of FIGS. 2 and 3;
[0017] FIG. 5 is a partially-exploded perspective view of an
alternative embodiment of a carriage assembly;
[0018] FIG. 6 is an enlarged exploded perspective view of a
retraction device useful with the carriage assembly of FIG. 5;
[0019] FIG. 7A is a partially-exploded perspective view of another
alternative embodiment of a carriage assembly;
[0020] FIG. 7B is a perspective view of a spring adjusting device
of FIG. 7A, taken from below;
[0021] FIG. 8 is a perspective view of a gravity take-up device,
taken from the side, top, and end thereof;
[0022] FIG. 9 is a perspective view of the gravity take-up device
of FIG. 8, taken from the side, top, and opposite end thereof;
[0023] FIG. 10 is a side elevation of the gravity take-up device of
FIG. 8;
[0024] FIG. 11A is a perspective view of the gravity take-up device
of FIG. 8, taken from the opposite side, top, and end thereof;
and
[0025] FIG. 11B is a perspective view of the gravity take-up device
of FIG. 11A, having a motor and gearbox installed thereon.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
[0026] Referring now specifically to the drawings and the
illustrative embodiments depicted therein, a roller transport
conveyor 20 includes a frame 21 having a pair of spaced-apart side
walls 22, a plurality of rollers 24 rotatably supported by
sidewalls 22, an endless drive belt 26 for rotating the rollers, a
gravity take-up 28 for maintaining a relatively constant tension on
drive belt 26, and a plurality of carriage assemblies 30 for
biasing drive belt 26 upwardly into frictional contact with rollers
24 (FIGS. 1 and 8). Gravity take-up 28 is capable of maintaining
tension in drive belt 26 without a source of electrical or
pneumatic or hydraulic power, as will be described in greater
detail below.
[0027] Carriage assemblies 30 include a support member 32, a
retraction device 34, a spring 36, and a contact member 38 (FIGS.
2A, 2B, 5, and 7A). Support member 32 is supported at side wall 22.
Contact member 38 is movably supported on support member 32, and is
vertically biased or adjustable thereon. A pair of wheels or
pulleys 33a, 33b are rotatably supported at contact member 38 for
supporting drive belt 26. It will be appreciated that any number of
pulleys may be provided at each carriage assembly for supporting
the drive belt, such as one pulley or three or more pulleys.
Retraction device 34 is mounted at support member 32, and engages a
lower end of spring 36. Spring 36 has a top portion 36a for
engaging contact member 38 and urging contact member 38 upwardly
relative to support member 32. Carriage assemblies 30, including
support member 32 and contact member 38, are more fully described
in commonly assigned U.S. Pat. No. 7,093,709 and U.S. Pat. No.
6,811,018, both of which are hereby incorporated herein by
reference.
[0028] Spring 36 may be a coil spring that is vertically oriented
to apply sufficient upward force to contact member 38 so as to urge
drive belt 26 upwardly into frictional contact with the lower
portions of rollers 24. Spring 36 is compressible or lowerable to
move contact member 38 downwardly and to permit drive belt 26 to
disengage from rollers 24, as will be described below. It will be
understood that other types of springs may be suitable for use in
place of coil spring 36. For example, leaf springs or resilient
rubber or polymer blocks may be used to provide substantially the
same function as spring 36 without departing from the spirit and
scope of the present invention.
[0029] Retraction device 34 facilitates the lowering of contact
member 38 by an operator, such as when the operator desires to
position the carriage for storage or transport, or to service
conveyor 20 such as by replacing rollers 24 or drive belt 26. In
the embodiment depicted in FIGS. 2A-4, spring adjusting device 34
is a contact member retainer 40 having a base 42, a projection 44
with a flange or clasp 46 for retaining contact member 38 in a
lowered position with spring 36 in a compressed state. A handle or
lever 48 is provided for disengaging clasp 46 from a catch 49 at a
lower side of contact member 38. A spindle 50 maintains the
alignment of spring 36. Base 42 is supported at support member 32
and includes a circular channel 52 for receiving the lower portion
of spring 36 (FIG. 4). Spindle 50 may include several projections
50a (FIG. 4), or may be a single-piece spindle 50' (FIG. 3) for
supporting spring 36 in a substantially vertical orientation.
[0030] Spring 36 is manually compressible under catch 49 by
lowering contact member 38 until clasp 46 engages a portion of
catch 49 at the lower side of contact member 38. Catch 49 is a flat
disc that is molded or formed at the lower side of contact member
38 and has a diameter greater than the diameter of spring 36. Catch
49 engages top portion 36a of spring 36 so that spring 36 supports
contact member 38 at catch 49. Clasp 46 extends laterally outward
from projection 44 a distance sufficient for clasp 46 to engage a
portion of catch 49 when contact member 38 is lowered. Lever 48
permits an operator to bend projection 44 radially outward and away
from catch 49 to release spring 36 from a compressed state to raise
contact member 38 from its lowered position and to permit spring 36
to urge contact member 38 upwardly. Projection 44 is sufficiently
strong and resilient to hold contact member 38 down and spring 36
in a compressed state while permitting projection 44 to flex and
disengage from catch 49 without breaking. It will be appreciated
that spring retainer 40 may be made from any sufficiently strong
and resilient material, such as plastic, and may be molded as a
single piece (FIG. 4), or formed unitarily with support member
32.
[0031] In another embodiment, as shown in FIGS. 5 and 6, retraction
device 34' is a telescoping assembly 54 having a base 56, a
rotatable inner telescoping member 58, and a spindle 60. Base 56 is
mounted at support member 32 and has a substantially cylindrical
passageway 62 that is adapted to receive rotatable inner
telescoping member 58. A pair of helical or spiral-shaped channels
64 are formed at an inner surface 66 of base 56, which defines the
outer radial extent of cylindrical passageway 62. Rotatable inner
telescoping member 58 has an outer surface 70 with a pair of
projections 68 extending radially outwardly therefrom. Rotatable
inner telescoping member 58 has an outer diameter that is at least
somewhat smaller than the inner diameter of cylindrical passageway
62 of base 56 to permit rotatable inner telescoping member 58 to
move freely relative to base 56. Radial projections 68 have a
projection distance and an angle that are complimentary with the
depth and angle, respectively, of helical channels 64. It will be
appreciated by those skilled in the art that rotatable inner
telescoping member 58 may be inserted into cylindrical passageway
62 of base 56 and radial projections 68 may be aligned with helical
channels 64 so that when rotatable inner telescoping member 58
engages base 56, the rotation of rotatable inner telescoping member
58 relative to base 56 will cause rotatable inner telescoping
member 58 to move axially vertically within base 56. Thus, it will
be understood that radial projections 68 perform a similar function
to conventional screw threads as projections 68 move along channels
64.
[0032] Alternatively, helical channels may be formed at a rotatable
inner telescoping member and projections formed at a base in order
to effect telescopic extension of the rotatable inner telescoping
member relative to the base. It will also be understood that,
optionally, inner telescoping member may be held stationary and the
base rotated relative to the inner telescoping member to effect
telescopic extension. It will be appreciated that channels having
varying non-helical shapes, such as vertical channels or channels
having a zigzag pattern, for example, may be used to permit
telescopic extension of a rotatable inner telescoping member
relative to a base or other telescoping member.
[0033] Rotatable inner telescoping member 58 may have a diameter
further corresponding to the diameter of a coil spring 36', similar
to spring 36, such that the spring's bottom end is supported at a
top surface 58a of rotatable inner telescoping member 58. Helical
channels 64 incorporate detents 72 at their upper ends for securely
holding rotatable inner telescoping member 58 at a raised position
(FIG. 5) when radial projections 68 engage detents 72. Thus, it
will be appreciated that rotatable inner telescoping member 58 is
telescopically raisable in base 56 by rotating rotatable inner
telescoping member 58 in a counterclockwise direction relative to
base 56 (when observed from above), and lowered by rotating inner
telescoping member 58 in a clockwise direction, relative to base
56. Inner telescoping member 58 may be grasped directly and rotated
by hand from below, for example, or may include a handle or tool
receiver (not shown) to facilitate rotation by hand or with a tool,
such as a screwdriver or wrench or the like.
[0034] Accordingly, it may be observed that when spring 36' is
installed at top surface 58a of inner telescoping member 58, the
lowering of rotatable inner telescoping member 58 by rotation in a
first direction (clockwise when observed from above) will cause
spring 36' to move to a lowered position, thus lowering contact
member 38. Similarly, rotation of rotatable inner telescoping
member 58 in a second direction (counterclockwise) moves spring 36'
upwardly to raise inner telescoping member 58, thus causing spring
36' to urge contact member 38 upwardly, and urging drive belt 26
into frictional contact with rollers 24.
[0035] In a third embodiment of the present invention, as shown in
FIGS. 7A and 7B, spring adjusting device 34'' is a telescoping
spring base 74 that is movably mounted to support member 32.
Telescoping spring base 74 has one or more locking members 76 that
each engages a corresponding recess or channel or groove 78 in
support member 32 and adjacent telescoping spring base 74. Further,
telescoping spring base 74 has a top surface or platform 80 for
supporting a spring 36'', similar to spring 36, for urging contact
member 38 upwardly.
[0036] Telescoping spring base 74 has a plurality of ribs 82 spaced
above locating tabs 84. Initially, ribs 82 move vertically in
grooves 78. When spring base 74 is fully raised, base 74 may be
rotated so that it receives a platform 85 of support member 32
between ribs 82 and tabs 84. Locking member 76 is a resilient
projection extending downwardly from platform 80 of telescoping
spring base 74. When base 74 is at the raised position and rotated
about 45 degrees in either direction, a lower portion of locking
member 76 extends outwardly from base 74 to engage recess 78 to
prevent further rotation and/or lowering of base 74 (FIG. 7A). A
spindle 84 is provided for maintaining spring 36'' in a vertical
orientation. Optionally, and as shown, telescoping spring base 74
may have a cylindrical recess 86 for receiving and partially
enclosing the spring 36''. Spring 36'' contacts and is supported by
a lower inner surface (not shown) of cylindrical recess 86 when
spring 36'' is installed therein. Telescoping spring base 74 may be
grasped directly and rotated by hand from below, for example, or
may include a handle or tool receiver 87 to facilitate rotation by
hand or with a tool, such as a screwdriver or wrench or the
like.
[0037] Accordingly, it may be observed that raising telescoping
spring base 74 and then rotating base 74 about 45 degrees so that
locking member 76 engages recess 78, causes spring 36'' to urge
contact member 38 upwardly so as to cause drive belt 26 to
frictionally engage and drive rollers 24. By pressing radially
inwardly on locking member 76, locking member 76 disengages from
recess 78 so that telescoping spring base 74 may be rotated about
45 degrees and then lowered vertically relative to support member
32 until contact member 38 is displaced downwardly, thus moving
drive belt 26 out of engagement with rollers 24.
[0038] Referring now to FIGS. 8-11B, gravity take-up 28 includes a
cable 88, a mass 90, and a plurality of pulleys or sheaves 92 for
routing cable 88 and for applying tension to drive belt 26. Mass 90
is suspended above a platform 94 of frame 21 by cable 88. Cable 88
is routed vertically upward from mass 90 to a first sheave 92a,
then horizontally to a second sheave 92b, then diagonally
downwardly to a third sheave 92c, from which cable 88 is routed
horizontally to a fourth sheave 92d, and finally to a winch
assembly 96 mounted to frame 21. Fourth sheave 92d is rotatably
connected to a bracket assembly 98, which is movably received in
channels 100a, 100b of guide members 102a, 102b (FIG. 9). A belt
pulley 104 is rotatably supported at bracket assembly 98, opposite
fourth sheave 92d, and has drive belt 26 reeved upon it. The range
of travel of bracket assembly 98 along guide members 102a, 102b is
approximately equal to the distance between mass 90 and first
sheave 92a when mass 90 is lowered to platform 94, and may be
longer or shorter depending on the application and size
constraints. It will be appreciated that the number of sheaves and
the routing of cable may be varied or changed according to the
particular application.
[0039] An aperture or window 105 is provided at a vertical plate
107 of frame 21, adjacent mass 90, to permit viewing of the height
of mass 90 above platform 94 so that an operator may readily
observe when mass 90 should be raised. A scale or indicator (not
shown) may be included at window 105 for more clearly indicating
the height of mass 90 above platform 94.
[0040] As best seen in FIGS. 8 and 9, winch assembly 96 includes a
spindle 106 rotatably mounted in a winch frame 108 with a
ratcheting device or pawl 110 pivotably mounted to frame 108 for
selective engagement with a gear 112 at an end portion of spindle
106. Cable 88 may be routed through a hole or a passageway 114 in a
vertical plate 116 of gravity take-up 28 and wound around spindle
106 of winch assembly 96. Pawl 110 may be manually-engaged,
gravity-engaged, or spring-biased, for example, to engage with gear
112 to prevent winch assembly 96 from releasing or paying out cable
88 and lowering mass 90. Winch assembly 96 may be used to
compensate for stretch in cable 88 and/or drive belt 26, and
further, permits the use of drive belts of various lengths.
[0041] Drive belt 26 is driven by an electric motor 122 supported
on frame 21. Motor 122 drives a pulley 124 via a gearbox 126 (FIG.
11B). Drive belt 26 is reeved around pulley 124, which frictionally
engages belt 26. Gearbox 126 converts rotary output from motor 122
by turning the axis of rotation by about 90 degrees and,
optionally, by reducing the speed of the output. It will be
appreciated that various power supplies may be used without
departing from the spirit and scope of the present invention. For
example, a hydraulic motor, pneumatic motor, combustion engine, or
the like may be used to drive drive belt 26, and may do so via
direct drive, drive shaft, or gearbox.
[0042] Thus, for example, drive belt 26 may be installed at roller
transport conveyor 20 and reeved around pulley 104 of gravity
take-up 28 while mass 90 rests upon platform 94 and cable 88 is
slack. Then, spindle 106 of winch assembly 96 is turned to draw
cable 88 into winch assembly 96, thereby raising mass 90 a desired
distance above platform 94. Over time, cable 88 and/or drive belt
26 may stretch, especially if they are new, and may wear such that
their respective lengths increase over time. It will be appreciated
that any increase in length of the drive belt 26 will result in a
corresponding movement of bracket assembly 98 along channels 100a,
100b, causing cable 88 to be fed downwardly from first sheave 92a,
such that mass 90 is lowered toward platform 94. Substantially
constant tension is maintained in drive belt 26 by maintaining mass
90 at a position spaced apart from and above platform 94.
Therefore, to maintain substantially constant tension in drive belt
26 and to prevent mass 90 from contacting platform 94, winch
assembly 96 may be used to wind cable 88 onto spindle 106, thereby
once again raising mass 90 relative to platform 94. Therefore, the
amount of belt stretch that can normally be accommodated is
typically primarily limited by the range of travel of bracket
assembly 98 along channel 100 of guide member 102.
[0043] Mass 90 may be fixed or adjustable in weight. It may be
adjustable by including a plurality of plates 118 connected to one
another by one or more fasteners 120. Thus, plates 118 may be added
or subtracted from mass 90 to adjust the desired amount of tension
in drive belt 26. Alternative masses are envisioned that may
include, for example, a concrete block or a holding tank for
containing a flowable medium such as dry sand or water. A holding
tank permits adjustment of the weight of the mass, and thus the
tension on the belt, by adding or removing the flowable medium to
or from the tank.
[0044] Thus, tension is imparted to cable 88 via gravity acting
upon mass 90. Cable 88 applies a resultant force F (FIG. 8) upon
fourth sheave 92d that is transmitted to drive belt 26 via pulley
104 and bracket assembly 98. The tension in cable 88 is
approximately equal to the weight of mass 90, minus any frictional
losses or other losses that may occur in gravity take-up 28. Winch
assembly 96 is operable to raise and lower mass 90 to service or
replace drive belt 26, for example, and to adjust for belt stretch,
cable stretch, and variations in the lengths of the cable and the
drive belt. Turning spindle 106 in a first direction causes second
end portion 88b of cable 88 to wind upon spindle 106 so that mass
90 is raised above platform 94 to apply force F to fourth sheave
92d and to place drive belt 26 in tension. Pawl 110 prevents cable
88 from unwinding from spindle 106. Releasing pawl 110 permits an
operator to turn spindle 106 in a second direction to unwind cable
88 from spindle 106 so that mass 90 is lowered toward platform 94.
When mass 90 contacts and is fully supported by platform 94, slack
is imparted to cable 88 and also to drive belt 26, whereupon drive
belt 26 may be removed from conveyor 20.
[0045] Accordingly, roller transport conveyor 20 provides carriage
assemblies 30 for raising drive belt 26 into frictional contact
with rollers 24 for driving the rollers. Springs provide the force
for urging drive belt 26 into frictional contact with rollers 24,
and therefore a separate electrical, hydraulic, or pneumatic
actuator and power source are unnecessary for raising the contact
member 38 to urge the drive belt 26 upwardly. Additionally, gravity
take-up 28 provides constant tension on drive belt 26 with a wide
range of adjustability to compensate for wear or stretch, and
further provides a simple method of adjustment.
[0046] The spring-supported carriage urges the drive belt, which is
driven by the electric motor, into frictional contact with the
undersides of conveying rollers for rotating the rollers. The
springs for supporting the carriages are adjustable and/or movable
to facilitate maintenance, setup, and transport of the conveyor.
The take-up maintains substantially constant tension in the drive
belt and is adjustable to compensate for significant belt stretch
or to accommodate belts of various lengths. The roller transport
conveyor is operable without need for electrical or hydraulic or
pneumatic power beyond that which may be used to drive the drive
belt and rollers.
[0047] Changes and modifications in the specifically described
embodiments may be carried out without departing from the
principles of the present invention, which is intended to be
limited only by the scope of the appended claims, as interpreted
according to the principles of patent law including the doctrine of
equivalents.
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